About half of the fructose intake of both mothers and children came from sweetened drinks and fruit juice.

Compared with the children of women who consumed the least sugar — an average of 21 grams a day — the children of those who had the most — 46 grams a day — had a 58 percent higher risk for asthma. (A 12-ounce can of Coca-Cola contains 39 grams of sugar.) The researchers controlled for maternal education, smoking and pre-pregnancy body mass index, as well as for the child’s B.M.I., age, sex and race.

A lead author, Sheryl L. Rifas-Shiman, of the department of Population Medicine at Harvard Medical School, said that the mechanism for the association remains unknown.